I'm not sure the pain-in-the-back argument is necessarily true. Even for many upright refrigerators, you must still bend over or crouch to get things from lower shelves and drawers. I've never felt inconvenienced removing things from my chest freezer. Also, my chest freezer has some sliding racks that make it great for organizing its contents. It seems possible that the pain-in-the-back argument is great for marketing, because it sounds like there could be some truth to it. I would argue that a person that has back trouble would likely only be able to use the chest level shelves in fridges, but they could just as easily use the top level racks in a chest freezer.

My guess for why traditional upright fridges could be seen as more convenient is because they take up less floor space for the amount of volume they provide. Also, upright fridges would be easier for small/short children to access. If floor space is less of a concern, and there is no need for small children to access the fridge, a chest-freezer-style fridge sounds like a brilliant idea. Next time I need a new fridge, I will seriously consider this as an option. Perhaps by then some contrarian manufacturers will realize how much sense this makes and I won't even need to convert a freezer myself.